The invention disclosed herein relates generally to mechanisms in which one member rotationally slips relative to another when applied torque exceeds a predetermined limit, and more particularly to a compact slip clutch whose slipping torque is adjustable without disassembly of the clutch mechanism.
Slip clutch mechanisms are required or desirable in a variety of applications for controlling the torque transmitted from one member to another. Examples include applications in which it is desired t prevent stalling of an electric motor in case the load being driven thereby becomes jammed, and/or in which it is desired to protect gear trains and other elements between a motor and load.
As a result of availability of improved materials and advances in motor design, motors and gear trains associated therewith have become increasingly compact, while being capable of delivering and transmitting increasing amounts of power. Such advances have made possible and created demands for further reductions in physical size. It has also become necessary to achieve greater precision in operating characteristics and parameters.
It is frequently desirable or necessary to provide a slip clutch feature in a compact and sometimes complex gear train. For such applications, the slip clutch must also be compact. In order to achieve the slipping torque precision required for some applications, it may be necessary to adjust the slipping torque after final assembly of the motor and gear train. Because of other design constraints, the slip clutch may be relatively inaccessibly located among other components. Especially in such a situation, it is desirable to be able to easily adjust the slipping torque without disassembly of the mechanism. It is also necessary for reliability that once the mechanism has been adjusted to provide the desired slipping torque, the adjustments not be subject to inadvertent changes.
It is known in relatively compact slip clutch designs to adjust the slipping torque by adding or removing shims between a retainer and a bias spring mechanism. This generally requires at least some disassembly and is undesirable for that reason. It is also known to adjust slipping torque by varying the compression of a bias spring by means of a threaded shaft or stud and mating nut. Such a design normally takes up more space along the axis of rotation than the removable shim design, and may be undesirable for that reason. In addition, the design of some gear systems is such that no shaft or stud is available for use with a torque adjusting nut.
The applicant has devised a compact slip clutch arrangement which avoids the above described disadvantages, and in which slipping torque is easily adjustable and securely maintained without requiring disassembly.